Our Diamond Nitro Rolls can be installed over a concrete floor. These rolls are non-porous, so if your concrete sweats, the moisture will get trapped under the rolls. We would recommend sealing your concrete to keep this from happening, but if you don't, it won't affect the flooring in any way. We would just recommend lifting the rolls from time to time to dry and clean them as the salts from the concrete will collect under the rolls. It will look white, but it is not mold, it's just salt.